My suggestions are mostly aesthetic and choice of wording.
If this isn't indicative of the character skill, we probably shouldn't refer to each level as a 'skill' level, or as 'Expert', 'Master', etc.
Since it's instead an indicator of specialisation or investment, call them levels of investment:
'Basic', as we currently have. It's fine.
'Focus' - your character puts time and effort into this trait.
'Purpose' - your character is driven by this trait. They have invested countless hours into their art.
'Definition' - your character defines themselves by this trait. No matter how skilled they are in anything else, it pales to their talent in this.
The names are not as glamorous as 'Master' or 'God', but I think they cause less confusion. It also cuts out the need to limit access to 'Definition' - if a tier 3 wanted to spend all their points to show they defined themselves by their training in kidou, good for them.